Motor fuel



iiii:

This invention relates to improvements in the suppression of surface ignition and reduction of octane requirement increase of leaded gasolines in the operation of internal combustion engines. More particularly, the invention provides an improved motor fuel and an improved method for preparing such fuel.

Current emphasis on high compression ratios and other high performance design features in gasoline engines of the internal combustion type, has tended to raise not only octane requirement but has created a situation where knock from surface ignition, often referred to as preignition, has become a limiting factor in engine design and operation. Knock induced by surface ignition appears to be a result of the use of o-rgano-lead compounds, and particularly tetraethyl lead, as the anti-knock agent in fuels of high performance value. When motor fuels containing lead are burned in internal combustion engines, deposits consisting of carbonaceous material and lead salts are continuously formed in the combustion chambers. These deposits are harmful in that they increase the octane requirement of the engine by inducing knock and causing surface ignition.

It has been proposed to provide a leaded motor fuel with a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon to minimize the tendency of deposits to promote surface ignition and increase octane requirement. This additive has proven very effective but it has been found that when diluting such a product so that it may be readily incorporated in gasoline the diluent seriously interferes with the effectiveness of the additive and in some instances the beneficial effect is completely nullified.

It is an object of this invention to provide an improved method of preparing a motor fuel for spark ignitioninternal combustion engines which contains an organolead anti-knock compound and a neutralized, alkali-metalcontaining reaction product of a phosphorus sulfide and a hydrocarbon. Another object is to provide a method of incorporating a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon in a gasoline mixture whereby the beneficial effects of the additive are not impaired. A more specific object is to provide a solvent for incorporating, in a motor fuel, the aforesaid neutralized reaction product, which solvent may be used in any desired amount without deleterious effects.

We have discovered that the above objects can be accomplished by providing a method of preparing a motor fuel for spark ignition-internal combustion engines which comprises the steps of adding to a gasoline mixture a minor amount of an organo-lead anti-knock compound, preferably tetraethyl lead, and a neutralized, alkali-metalcontaining reaction product of a phosphorus sulfide and a hydrocarbon which neutralized reaction product is diluted before incorporation with the gasoline mixture with an aromatic hydrocarbon solvent boiling in the range of from about 100 to 450 F. and preferably in the range of from about 200' to about 400 F. The neutralized reaction product is added to the fuel in an amount sufiicient to give a mol ratio of phosphorus to lead in the range of from about 0.01 to about 2.0. The phosphorus sulfide is preferably phosphorus pentasulfide I HQ 3,052,530

Patented Sept. 4, 1962 and the hydrocarbon can preferably be a polymer of a mono-olefin of less than 6 carbon atoms, which polymer has a molecular weight in the range of from about 125 to about 50,000. The preferred alkali metal is potassium although other alkali metals such as sodium and lithium can be suitably employed. The aromatic hydrocarbon solvent can be any of the aromatics falling in the gasoline distillation range and preferably a mixture of aromatics having about 8 carbon atoms.

The motor fuel can contain tetraethyl lead at a concentration of from about 0.5 ml. to about 5 ml. or more per gallon. The concentration of tetraethyl lead may be varied as is usual with the engine and its use.

The motor fuels will preferably be gasoline but may be any other combustible liquid of suitable volatility commonly employed as fuel for internal combustion-spark ignition engines, including paraffiuic, naphthenic and aromatic hydrocarbons, isooctane and mixtures of isooctane with other suitable liquid hydrocarbons. The boiling point of such fuels should be in the range of from about F. to about 500 F. and preferably in the range of from about 150 F. to about 400 F. Such motor fuels may also contain anti-oxidants, stabilizers, dyes, anti-icing agents, lead scavenging agents and/ or other compounds which are commonly employed in leaded motor fuels.

We can also provide, in accordance with our invention, an additive mixture which comprises essentially an arcmatic hydrocarbon solvent boiling in the range of from about 100 to about 450 F., preferably C aromatics, an organo-lead anti-knock compound and a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon, the mol ratio of phosphorus to lead in the mixture being from about 0.01 to about 2.0. Sufficient aromatic hydrocarbon solvent should be employed to obtain desirable fluidity. For example, the solvent can be employed in the range of from about 25% to about 95% or more based on the total weight of mixture. Although the solution of the neutralized, alkalimetal-containing reaction product of a phosphorus sulfide and a hydrocarbon can be added to the motor fuel separately from the organo-lead, it may be desirable to add it simultaneous therewith. The organo-lead compound is preferably tetraethyl lead. The conventional tetraethyl lead fluid contains small amounts of halo-hydrocarbon lead scavenging agents, dyes, hydrocarbon diluents, etc., but the phosphorus to lead ratio is based on the tetraethyl lead content thereof.

In the preparation of the phosphorus sulfide-hydrocarbon reaction product, the hydrocarbon is reacted with a phosphorus sulfide such as P 8 P 8 P 8 or other phosphorus sulfides, and preferably phosphorus pentasulfide, P285.

The hydrocarbon constituent of this reaction is preferably a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular weight mono-olefinic hydrocarbons or iso-mono-olefinic hydrocarbons, such as propylenes, butylenes and amylenes, or the copolymers obtained by the polymerization of hydrocarbon mixtures containing iso-mono-olefins and mono-olefins of less than 6 carbon atoms. The polymers may be obtained by the polymerization of these olefins or mixtures of olefins in the presence of a catalyst such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride or other similar halide catalysts of the Friedel-Crafts type and preferably have a molecular weight in the range of from about to 50,000.

Other preferred olefins suitable for the preparation of the hereindescribed phosphorus sulfide reaction products are those having at least 8 carbon atoms in the molecule.

Essentially paraffinic hydrocarbons such as bright stock residuums, lubricating oil distillates, petrolatums, or paraifin waxes, can be used. There can also be employed the condensation products of any of the foregoing hydrocarbons, usually through first halogenating the hydrocarbons, with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Also contemplated within the scope of the present invention are the reaction products of a phosphorus sulfide with an aromatic hydrocarbon, such as, for example, benzene, naphthalene, toluene, xylene, diphenyl and the like or with an alkylated aromatic hydrocarbon, such as, for example, benzene having a 'alkyl substituent having at least four carbon atoms, and preferably at least eight carbon atoms, such as long chain paraffin wax.

While the aforesm'd hydrocarbon constituents of the phosphorus sulfide-hydrocarbon reaction product are all effective in accordance With the invention, it is not to be implied that all are necessarily exactly equivalent in their effectiveness. Although the function of the hydrocarbon is not completely understood, its primary purpose is to impart solubility, in gasoline, to the reaction product.

In general, the preparation of the phosphorus sulfidehydrocarbon reaction pro duct in accordance with the present invention is carried out in the following manner:

The hydrocarbon, such as, for example, an olefinic polymer of the desired molecular weight, is reacted with from about 1% to about 50%, and preferably from about 5% to about 25%, of a phosphorus sulfide, e.g., P 8 at a temperature of from about 200 F. to about 600 F. in a non oxidizing atmosphere, such as, for example, an =atmosphere of nitrogen. The reaction is carried out for from about one to about ten hours or more, and preferably for about five hours. The phosphorus sulfide-hydrocarbon reaction can, if desired, be carried out in the presence of a sulfurizing agent such as elemental sulfur or a halide of sulfur. The reaction product obtained can, if desired, then be hydrolyzed at a temperature of from about 200 F. to about 500 F., and preferably at a temperature of 300 F. to 400 F., by a suitable means, such as, for example, by introducing steam through the reaction mass. The hydrolyzed product containing inorganic phosphorus acids formed during the hydrolysis can then be contacted with an adsorbent material such as Attaulgus clay, fullers earth and the like at a temperature of from about 100 F. to about 500 F. and the treated hydrolyzed product filtered to obtain a filtrate substantially free of inorganic phosphorus acids and low molecular weight organic phosphorus compounds.

The reaction product of a phosphorus sulfide and a hydrocarbon, preferably treated in the above manner with or without hydrolysis and clay treating, is then neutralized with an alkali metal compound. Although it is not essential, the product is preferably diluted with about an equal volume of an aromatic hydrocarbon solvent, described hereinafter, before neutralization to facilitate mixing and handling. The neutralization step with an alkali metal is carried out with a suitable basic compound such as the metal hydroxide, carbonate, oxide or sulfide, such as potassium hydroxide, sodium hydroxide, lithium oxide or the like. It is preferable, however, to use potassium or hydroxide.

The basic alkali metal compound may be admixed directly with the phosphorus sulfide-hydrocarbon reaction product, dissolved in water or an alcohol-water mixture and then be admixed therewith, or a slurry of the alkali metal compound in an aromatic hydrocarbon solvent, described hereinafter, can be prepared and then admixed therewith. This reaction is carried out preferably in a non-oxidizing atmosphere at an elevated temperature from about 100 F. to about 400 F.

After preparation of the alkali-metal-containing reaction product as described above, the mixture may be diluted with an aromatic hydrocarbon solvent, described hereinafter, to obtain desirable fluidity. Without dilution the mixture is quite viscous and is not readily soluble in gasoline, thus it is desirable to add hydrocarbon solvent to obtain desirable fluidity. At about 10 volumes of solvent per volume of alkali-meta'l-cont-aining reaction prod uct, the mixture is readily soluble in gasoline and may be handled easily. Additional quantities of solvent over and above this amount can be used, however, from an eco nomic standpoint this is generally not desirable. Smaller quantities of solvent can also be used, however, at con centrations of less than about 1:1 the mixture is quite viscous difiicult to handle.

As pointed out hereinbefore, the aromatic hydrocarbon solvent preferably has a boiling point in .the range of from about 200 to about 400 F. Such a solvent may be o tained, for example, by recovering, by distillation, the C aromatic fraction of the product obtained from the catalytic reforming of a naphtha.

Other preferred, aromatic hydrocarbon solvents are those resulting from the solvent extraction of hydrocarbon mixtures in the gasoline distillation range to remove aromatic compounds. The solvents employed to remove such aromatic compounds are well-known to the art; thus, for example, ethylene glycol, diethylene glycol and mixtures thereof have been employed for the purpose. The anomatic hydrocarbon solvents can also be obtained by extractive distillation of hydrocarbon mixtures in the gasoline distillation range employing, for example, phenol, sulfur dioxide and the like. Pure aromatic hydrocarbons having a boiling point in the gasoline distillation range may also be employed, however this is generally not economically feasible.

As pointed out hereinbefore, the neutralized, alkalimetal-containing-reaction product of a phosphorus sulfide and a hydrocarbon can be diluted with an aromatic hydrocarbon solvent and incorporated directly in a leaded gasoline, or it may be admixed with tetraethyl lead to fiorm an additive mixture which may be incorporated in a motor fuel.

As specific embodiments 'of our invention, the following examples are given by way of illustration and are not intended as a limitation of our invention:

EXAMPLE I Butylene polymer (of about 750 mean molecular Weight) was reacted with about 15% P 8 and 2% sulfur at a temperature of about 400 F. for five hours in an atmosphere of nitrogen. The product was then neutralized with about 9% potassium hydroxide dissolved in an equal amount of water at a temperature of about 400 F. Following neutralization the product was steamed at 400 F. for one hour and then stripped with nitrogen for about one hour at 400 F. to remove any remaining water. This product had a sulfur content of 1.16%, potassium content of 3.16% and a phosphorus content of 2.70%. The product was then diluted with about 10 volumes of a solvent extracted SAE 5 lubricating oil.

EXAMPLE II The steamed and stripped neutralized reaction product of Example I was diluted with about 10 volumes of an aromatic solvent containing about 86% C aromatics, about 5% C aromatics, about 1% toluene and about 8% nonaaromatics.

The diluted, neutralized, alkali-metal-containing-P S butylene polymer reaction products thus obtained were incorporated in a premium gasoline, containing 3 milliliters of tetraethyl lead per gallon, in an amount sufiicient to give a 11101 ratio of phosphorus to lead of 0.13, and the fuels were evaluated for hours in a single cylinder, 'four cycle, overhead valve, liquid cooled engine having a 2% inch bore and a 3% inch stroke with a displacement of 17.6 cubic inches and which is equipped with an integral jacket condenser for coolant temperature control and electric heaters in the base for oil temperature control.

Operating conditions were as follows:

Cycle Conditions:

Time, sec

45 a No Air/fuel ratio i Surface ignition rates were determined and also the octane requirement increase. As shown in Table I, such data were obtained using the base leaded fuel containing 3 cc. TEL/gal, and the same leaded fuel with the additives of Examples I and II at a concentration sufficient to give a mol ratio of phosphorus to lead of 0.13; the solvent concentration in the total fuel mixture was thus about 0.11% Table I also includes data of the additive of Example I diluted with about 40 percent by weight of solvent extracted 5W oil used in amount to give approximately the same P/ Pb mol ratio; this more concentrated additive mixture was less fluid and dissolved less readily in leaded fuel at room temperature, but when lubricating oil is employed as the solvent, it is desirable to minimize the amount thereof in the motor fuel.

Table I Additive None Ex. I Ex. II Solvent None Solvent Extracted 5W Oil Solvent Concentration, percent 0.01 0.11 0.11 M01 Ratio, PIPb 1 0.10 0.13 0.13 Surface Ignition, Counts per hour. 304 177 306 211 Octane Requirement Increase 17.0 18.0 18.0 14. 5

The test data is Table I show that using the lubricating oil solvent at low concentration provides an effective additive but that further dilution therewith to obtain an additive mixture which is more readily handled and easily dissolved in the gasoline results in a fuel which has no beneficial effect upon surface ignition or octane requirement increase. However, when employing an aromatic hydrocarbon solvent in accordance with our invention (Example II) both octane requirement increase and surface ignition characteristics are improved even though large amounts of our solvent are employed.

Although the examples illustrate the effect of our additive mixture at a phosphorus to lead ratio of 0.13, we have observed that the ratio can be varied within rather wide limits and that by so doing the elfectiveness with respect to either octane requirement increase or surface ignition may be varied. Thus at lower ratios of phosphorus to lead in the defined range, surface ignition can be improved relatively while at higher ratios in the defined range greater improvement of octane requirement increase is obtained.

Although only a potassium containing reaction product has been used in the foregoing examples, we have observed that the same beneficial effect can be obtained when employing lithium or other alkali metals.

Percentages given herein and in the appended claims are weight percentages unless otherwise noted.

While we have described our invention by reference to specific embodiments thereof, the same are given by way 6 of illustration. Modifications and variations will be apparent from our description to those skilled in the art.

We claim:

1. A motor fuel for spark-ignition internal combustion engines comprising a major amount of a hydrocarbon mixture boiling in the gasoline distillation range, and an additive mixture comprising essentially from about 0.5 cc. to about 5 cc. per gallon of said hydrocarbon mixture of tetraethyl lead, a neutralized alkali metal-containing reaction product of a phosphorus sulfide and a hydrocarbon having a molecular weight within the range from about 125 to about 50,000, the amount of said alkali metalcontaining reaction product being suflicient to give a mole ratio of phosphorus to lead in the range of from about 0.01 to about 2, and from about 25% to about based on the total weight of said additive mixture, of an aromatic hydrocarbon solvent having a boiling point in the range of F. to 450 F., said alkali metal-com itaining reaction product being prepared by reacting said hydrocarbon with from about 1% to about 50% of said phosphorus sulfide at a temperature of from about 200 F. to 600 F., and neutralizing the resultant reaction product with a basic alkali metal compound.

2. An additive mixture for gasoline which comprises essentially from about 25% to about 95%, based on the total weight of said mixture, of an aromatic hydrocarbon solvent having a boiling point in the range of from about 100 F. to about 450 F., tetraethyl lead compound in an amount sufficient to give from about 0.5 cc. to about 5 cc. per gallon of gasoline, and a neutralized alkali metalcontaining reaction product of a phosphorus sulfide and a hydrocarbon having a molecular weight within the range from about to about 50,000, said neutralized reaction product being present in an amount sufficient to give a mole ratio of phosphorus to lead in the range of from about 0.01 to about 2.0, said alkali metal-containing reaction product being prepared by reacting said hydrocarbon with from about 1% to about 50% of said phosphorus sulfide at a temperature within the range of from about 200 F. to about 600 F. and neutralizing said reaction product with a basic alkali metal compound.

3. The composition of claim 2 in which the phosphorus sulfide is phosphorus pentasulfide and the hydrocarbon is a polymer of a mono-olefinic hydrocarbon having less than 6 carbon atoms and which polymer has a molecular weight of from about 125 to about 50,000.

4. The composition of claim 2 in which said aromatic hydrocarbon solvent is essentially a mixture of aromatic hydrocarbons having 8 carbon atoms.

5. The composition of claim 2 in which said alkali metal is potassium.

6. The composition of claim 2 in which said alkali metal is lithium.

References Cited in the file of this patent UNITED STATES PATENTS 2,066,234 Sloane et al Dec. 29, 1936 2,398,281 Bartholomew Apr. 9, 1946 2,439,819 Musselman Apr. 20, 1948 2,439,820 M-usselman Apr. 20, 1948 2,534,217 Bartleson Dec. 19, 1950 2,712,528 Hill et al July 5, 1955 2,726,942 Arkis et a1 Dec. 13, 1955 2,794,722 Bartleson June 4, 1957 

1. A MOTOR FUEL FOR SPARK-IGNITION INTERNAL COMBUSTION ENGINES COMPRISING A MAJOR AMOUNT OFA HYDROCARBON MIXTURE BOILING IN THE GASOLINE DISTILLATION RANGE, AND AN ADDITIVE MIXTURE COMPRISING ESSENTIALLY FROM ABOUT 0.5 CC. TO ABOUT 5 CC. PER GALLON OF SAID HYDROCARBON MIXTURE OF TETRAETHYL LEAD, A NEUTRALIZED ALKALI METALI-CONTAINING REACTION PRODUCT OF A PHOSPHORUS SULFIDE AND A HYDROCARBON HAVING A MOLECULAR WEIGHT WITHIN THE RANGE FROM ABOUT 125 TO ABOUT 50,000 THE AMOUNT OF SAID ALKALI METALCONTAINING REACTION PRODUCT BEING SUFFICIENT TO GIVE A MOLE RATIO OF PHOSPHORUS TO LEAD IN THE RANGE OF FROM ABOUT 0.01 TO ABOUT 2, AND FROM ABOUT 25% TO ABOUT 95% BASED ON THE TOTAL WEIGHT OF SAID ADDITIVE MIXTURE, OF AN AROMATIC HYDROCARBON SOLVENT HAVING A BOILING POINT IN THE RANGE OF 120*F. TO 450*F., SAID ALKALI METAL-CONTAINING REACTION PRODUCT BEING PREPARED BY REACTING SAID HYDROCRBON WITH FROM ABOUT 1% TO ABOUT 50% OF SAID PHOSPHORUS SULFIDE AT A TEMPERATURE OF FROM ABOUT 200* F. TO 600*F., AND NEUTRALIZING THE RESULTANT REACTION PRODUCT WITH A BASIC ALKALI METAL COMPOUND. 